Combustion chamber liner construction



June 0, 1964 E. w. WATERS ETAL COMBUSTION CHAMBER LINER CONSTRUCTION Filed Sept. 26. 1961 INVENTOR-f. fl ffff M M97525 United States Patent 3,138,930 COMBUSTION CHAMBER LINER CONSTRUCTION Everett Wilher Waters, Lynnfield, Mass., and Thomas Chase Campbell, Fairfield, Ohio, assignors to General Electric Company, a corporation of New York Filed Sept. 26, 1961, Ser. No. 140,827 2 Claims. (Cl. 6039.65)

This invention relates generally to combustion apparatus and, more particularly, to an improved liner con struction for use in a jet engine combustion chamber.

There are a number of types of jet propulsion engines which utilize expanded and accelerated gases ejected through a nozzle to cause a reaction to produce thrust and move a vehicle in which the engine is mounted in a direction opposite that of the ejected gases. Typical of these jet engines is the so-called turbo-jet, which can be further differentiated into two general types, namely, the centrifugal-flow and the axial-flow engine. The basic components of each of these two engines are exactly the same, the primary difference between the two being the type of compressor used to supply compressed air to the engine combustion system. In addition to the compressor and combustion sections, each of these engines includes a turbine section (hence the name turbo-jet), an exhaust section, and, in some cases, a thrust augmentation, or afterburning combustion section. Although the following description relates to an axial-flow turbojet engine, it will be appreciated that the teachings of the invention are not limited thereto and may be applied to other types of jet engines.

In the combustion section of an axial-flow turbojet engine, air is mixed with fuel and ignited to provide the expansion which causes the air mass entering the inlet of the engine and delivered from the compressor to accelerate. Briefly, there are three basic types of axial flow combustors, namely: the can type; the annular type; and the can-annular type. The three types differ mainly in physical configuration, i.e., the can and can-annular types having small, individual liners, or cans in addition to a large annular casing structure. Until recently, primary utilization has been of the can type, but with the advent of lighter-Weight, high-intensity type combustion systems for supersonic jet engines, the fully annular combustor has come into greater prominence. The annular type has the advantages of efiicient air and gas handling and the most eflicient usage of the available space, i.e., less diameter for the same mass air flow, in addition to the fact that the amount of sheet metal surface needed to enclose the required volume of the combustion chamber is lower in the annular than in other types, which results in lighter Weight. However, the lower degree of curvature of the annular construction, as compared to the can type, has made it more susceptible to distortion.

Besides attempting to solve the distortion problem, since the combustion section is by nature more susceptible to repair and replacement, investigators have been searching for a construction which will provide ease of assembly and disassembly of the combustor without the need for incurring a major engine teardown. Thus, means have been suggested to facilitate the disassembly of the combustor, including the use of horizontally split outer combustion chamber casings with or without internal combustor liners, or cans, also consisting of more than one section. Other methods have been devised, either alone or in combination with the ease of replacement feature, for combating the problem of distortion mentioned above, such as constructing the outer portion of the combustor liner of a series of relatively small (in relation to the overall chamber diameter) arcuate segments pinned or hinged together. In addition, a variety of quick discon- 3,138,930 Patented June 30, 1964 nect type of arrangements have been suggested for mating the liner and casing sections.

The present invention has to do with an improved, fully annular combustion chamber liner construction capable of quick and easy removal and/ or installation in a jet engine and at the same time insuring the reliable operation of a large diameter, high-intensity type of combustion system. Accordingly, the primary object of the present invention is to provide an improved combustion chamber construction featuring an easily replaceable liner, in the event the liner wears out or becomes damaged through usage, which construction is of a simple type involving a few easily produced and assembled parts. A further object of the invention is to assure the maintenance of sufficient structural integrity of such a liner in order that it can withstand the extremely hot temperatures of the combustible gas stream normally present in aircraft capable of supersonic operation.

Briefly stated, in accordance with one of the illustrated embodiments of our invention, we provide a fully annular, horizontally-split combustion chamber liner construction, including means supporting the liner from a split outer casing which compensates for thermal expansion of the liner during operation of the combustor and for loads developed on the liner by interruption of its natural annular shape due to the horizontal split, and featuring a joint construction for use along the horizontal split line which preserves the structural continuity and integrity of the liner without presenting an obstruction to cooling and diluting airflow in the liner.

The features of our invention which we believe to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and in method of operation, together with further objects and advantages thereof, can best be understood With reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is an end view of a fully annular, axialflow jet engine combustion section utilizing the present invention.

FIGURE 2 is a side view, partially in cross section,

illustrating generally the manner in which the liner is positioned within the outer combustor casing.

FIGURE 3 is an enlarged, fragmentary side view of a section of the liner illustrating, in more detail, the way in which the liner may be attached to the outer casing wall.

FIGURE 4 is a fragmentary end view, partially in cross section, further illustrating the attachment structure of FIGURE 3.

FIGURE 5 is an enlarged, fragmentary, end view of the feature of the joint structure between the half-sections of the liner.

Turning now specifically to the drawings, FIGURE 1 shows the end view of the annular main combustion chamber construction for use in an axial-flow turbojet engine. While the main combustor has been utilized for purposes of description, it should be understood that the teachings of the invention are not limited thereto and'may equally be applied to a thrust augmenting combustion chamber construction. The combustor disclosed includes a pair of outer casing halves 12-12, formed by splitting the casing horizontally at 13. Centrally of the combustor is an inner casing 14, which, together with the outer casing, forms a space for reception of the annular combustor liner indicated generally at 15. The outer portion of the liner, like the outer casing, is horizontally split to form liner halves 16-16. Located concentrically within the outer liner halves, and without the inner casing, is the inner liner wall indicated at 17. Compressed air from the compressor (not shown) enters the combustion section of the engine through a diffuser section, indicated generally at 18 in FIGURE 2. The air, already heated by compression, is mixed with fuel supplied by a fuel injector nozzle 20. Suitable ignition means (not shown) may be provided to ignite the hot fuel/air mixture. The combustible hot gas stream then exits from the combustion section at 22, passing through a turbine nozzle and out an exhaust nozzle (not shown).

Turning now to a description of our invention concerning the feature of ease of assembly and disassembly of the so-called hot parts of the combustion section, it will be seen from the drawings that each outer liner half 16 may comprise a plurality of axially arranged semi-circular segments, indicated generally at 24. Indicated at 26, 27, and 28, respectively, are the forward, middle, and rear portions of one of the semi-circular segments. It will be noted that the forward and rearward portions, or ends of adjacent segments overlap by reason of the middle portion being angled inwardly. The ends are permanently joined by means of corrugated, or zig-zag strips 30, affixed to adjacent ends by suitable means, such as welding or brazing. The above-described construction is merely typical and the invention should liner 15 for proper combustion, this cooling, or secondary flow protects the thin-walled semi-circular segments 24 from burning out by the process of film cooling. This is accomplished by means of a thin film of cooling air from the openings 34 flowing over the inner surfaces of the liner segments.

It will also be noted from the drawings that the semicircular segments, and thus each liner half, includes a plurality of convolutions 36. It is, of course, well known that a cylinder will be somewhat self-supporting due to circumferentially extending hoop stresses, for example. However, with the need for splitting thevannular combustor liner to facilitate ease of replacement without the necessity of tearing down'the entire engine, most of the structural continuity of the liner will be lost because of the splitting (all of the structural continuity being lost immediately adjacent the joint). Splitting it into two halves has been found to be preferable to splitting the liner into a number of smaller pieces for reasons of strength retention, economy of manufacture, and ease of assembly, among other things. The convolutions, or corrugations, therefore, will add strength to each of the liner halves. Splitting the liner in such a manner creates a problem, however, in the design of the axially extending joint between the two liner halves since, while it is necessary to preserve as much of the structural continuity of the liner as possible, at the same time it is highly desirable to assure that there will not be any undue obstruc tion to the continuity of the liner film-cooling air.

A specific feature of the present invention, therefore, concerns the structure of the axially-extending joint between the liner halves. As seen in FIGURE 5, the stepped or segmented outer liner halves 1616 include a pair of axially extending end flanges, indicated generally at 3$-38. Each of the end flanges includes a middle portion 40 and a laterally-bent end portion 42. (Due to the overlapping of the ends 26 and 28 of the semicircular segments, the end flanges 3838 assume a stepped or offset configuration, when viewed in the axial direction.) Attached along either side of the juncture of the split outer casing sections 1212 are a pair of clip members, indicated generally at 44-44. These members are securely aflixed to the outer casing and include oppositely directed portions 46-46 spaced from the outer casing wall and extending substantially parallel thereto. With the outer casing sections joined it will be noted that the clip members form a box, or channellike structure having a slotted, axially-extending opening 48. When the liner halves 16f.6 are joined, the laterally-bent end portions 4-242 of the end flanges 38-38 are located within the interior of the box, or channellike structure formed by the clip members 44-44, with the middle portions -40 of the end flanges being in abutment and extending through the slotted opening 48. In addition to the fact that the casing-to-liner half attachments, hereinafter fully described, help to locate the position of the end flanges in abutment, the fact that the end-flanges necessarily have a spring-like quality, due to the liner halves being constructed of relatively thin sheet metal, aids in maintaining a fluid-tight joint at the endflanges. Also, the relatively high pressure of the secondary, or cooling air which is caused to flow in the area 50of the combustor between the outer casing 12 and outer liner 16 will tend to maintain the. end flanges in abutment, as, indicated by the dotted arrows in FIG- URE 5 depicting the pressure exerted by the cooling air.

Another feature of our invention is concerned with the method by which the outer liner halves may be attached to the outer casing. FIGURES 3 and 4-, in particular, illustrate a typical pin, or hinge type connection, indicated generally at 56. Specifically, FIGURE 4, shows one of a plurality of substantially V-shaped brackets 58 depending from the inner Wall 59 of the outer casing 12. The bottom portion 60 of each bracket is generally rounded to form a trough. Identical brackets 61 are provided on the outer surface 62 of the outer liner wall 16, the brackets preferably being located at the apices of the convolution 36. FIGURE 3 illustrates the fact that these pluralities of brackets are interspersed, with the rounded, or trough-like portions of each of the plurality of brackets on the outer casing extending radially inward beyond the rounded, or trough portions of each of the pluralities of brackets extending radially outward from the outer liner. Thus, as seen in FIGURE 4, when axially aligned, the brackets form a passageway 64 extending axially of the annular combustor. Loosely received within this passage is a rod or pin 65, which, when thus received, interlocks the brackets of the casing and liner. Because of the loose reception of pin, and its size and configuration and the configuration of the brackets, if during operation of the combustor differential thermal expansion should cause relative movement between the outer liner and casing, the arrangement just described permits relative motion between the pluralities of the brackets, as indicated by the solid arrows in FIG- URE 4.

Thus, an important feature of the invention will be seen to reside in the fact that the axially-extending, flexible end-flange joint structure and cooling arrangement permits this relative motion to exist Without loss of liner continuity or creation of undesirable obstructions to cooling air flow. In addition, the joint structure permits a liner-to-casing attachment whereby at no place is the liner rigidly fastened to the casing in a manner which would prevent differential thermal expansion to take place in a free and natural manner. Moreover, with the fit between the liner halves being tightly maintained, no convection or radiation of hot gases will occur adjacent to the axially-extending liner split line. By providing a spaced fit of the laterally-bent end portions 42-42 of the end flanges in the box, or channel-like area formed by the clip members, 44-44, cooling gas will be permitted to circulate around passages erebetween in the manner indicated by the solid arrows in FIGURE 5. However, should the flanges tend to separate slightly because of pressure changes or by reason of an unusual amount of differential thermal expansion so that all the surfaces of the flanges become exposed to both convection and radiation from the hot combustion gases, due to the pressure drop which will exist across the joint, cooling air will flow around the end portions and down between the adjacent radially extending middle portions 40-40, thus film cooling the joint in a manner similar to the liner proper. Our novel joint design therefore makes possible an axially-split liner wherein the joint does not present any obstruction to the continuity of the liner film-cooling air flow under any and all operating conditions, as it will be understood that any interruption of the film cooling flow at the joints between liner sections would cause the joints to become over-temperatured and, consequently, introduce the chance of failure of the liner. In addition, the piano-hinge type connections are so oriented at the apices of the convolutions that they will absorb side loads on the liner halves, which would normally be developed by reason of the interruption of the natural annular continuity of the convoluted liner to minimize any tendency for the liner to separate or become disengaged at the joint. Although pin, or piano-hinge connections have been shown, it should be understood that our axially-extending, filmcooled liner slip joint will be suitable for use with, and actually facilitate the adoption of, other types of flexible liner-to-casing attachments with all their benefits.

Thus, the applicants have provided means for axially splitting a combustor liner Wall which preserves the structural integrity of the liner at the points of discontinuity of the annular shape, while allowing for axial and radial diflerential thermal expansion between the liner and the casing, and providing full film cooling of both the liner and the axial-extending joint even in the event that, during operation of the combustor, the liner end flanges should become separated.

In describing our invention, it is our intention to cover all changes and modifications of the example of the invention herein chosen for purposes of disclosure, which do not constitute departures from the scope of the invention as pointed out in the following claims;

We claim:

1. A combustion chamber construction including: an outer casing, said casing comprising a plurality of sections; an annular liner spaced within said casing, said liner including a plurality of sections aligned with said casing sections; supporting means flexibly attaching said liner sections to said outer casing, said supporting means permitting freedom of relative movement between the liner sections and the casing to compensate for thermal expansion of said liner during operation of the combustion chamber; and means for joining said liner sections along axially extending edges thereof including a flange on each of said edges having a laterally-bent end portion and a radially-extending middle portion, pairs of clip members, one member of each pair of clip members being secured to one of an abutting casing section adjacent the axially extending edge thereof, said clip members having oppositely-extending portions spaced from and parallel to the inner surfaces of said outer casing sections to form a channel therewith, the bent end portions of said liner flanges being received within said channel, with respective ones of said flange bent end portions being radially aligned with respective clip member oppositelyextending portions in order that radially-aligned casing and liner sections are removable as a unit, said supporting means being arranged and located so that said middle portions of said flanges are normally in abutment to seal the joint between said liner section flanges and said bent end portions are centered in said channel to create flow passages for cooling fluid, said fluid acting to help maintain said flanges in abutment.

2. A combustion chamber for an axial-flow gas turbine engine including: an outer casing, said casing comprising a pair of half-sections; an annular liner spaced within said casing, said liner forming a flow passage with said casing for fluid under pressure, said liner including a pair of convoluted half-sections, each of said convoluted half-sections comprising a series of semi-circular segments axially arranged with overlapping upstream and downstream ends, joining strips located between said overlapping ends and rigidly securing adjacent segments together in a manner such as to permit pressurized cooling air in said flow passage to be introduced into said liner; supporting means attaching said liner half-sections to said outer casing half-sections including a first plurality of substantially V-shaped brackets secured to said liner half-sections at the apices of said convolutions, a second plurality of substantially V-shaped brackets secured to the inner walls of said outer casing half-sections, the brackets of said first and second pluralities, respectively, extending radially toward each other and being interspersed to form an axially-extending passageway positioned approximately in the center of said flow passage, a rod loosely received in said bracket passageway interlocking said brackets and providing freedom of relative movement between said convoluted half-sections and said outer casing to compensate for differential thermal expansion of said liner and the outer casing during operation of the combustor; and means joining said liner halfsections along axially extending edges thereof including a flange on each said edge having a laterally-bent end portion and a radially-extending middle portion, a pair of clip members located at each liner half-section joint, one member of each pair being secured to one of the abutting casing half-sections radially aligned with a liner halfsection adjacent the axially-extending edge thereof, said clip members having oppositely-extending portions spaced from and parallel to the inner surfaces of said casing sections to form a channel therewith, the bent end portions of said flanges being received in said channel, with respective ones of said flange bent end portions being radially aligned with respective clip member oppositelyextending portions in order that radially-aligned casing and liner half-sections are removable as a unit and being spaced from said oppositely-extending clip member portions to provide passages for the fiow of said pressurized fluid to film cool said flanges and said clip members.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A COMBUSTION CHAMBER CONSTRUCTION INCLUDING: AN OUTER CASING, SAID CASING COMPRISING A PLURALITY OF SECTIONS; AN ANNULAR LINER SPACED WITHIN SAID CASING, SAID LINER INCLUDING A PLURALITY OF SECTIONS ALIGNED WITH SAID CASING SECTIONS; SUPPORTING MEANS FLEXIBLY ATTACHING SAID LINER SECTIONS TO SAID OUTER CASING, SAID SUPPORTING MEANS PERMITTING FREEDOM OF RELATIVE MOVEMENT BETWEEN THE LINER SECTIONS AND THE CASING TO COMPENSATE FOR THERMAL EXPANSION OF SAID LINER DURING OPERATION OF THE COMBUSTION CHAMBER; AND MEANS FOR JOINING SAID LINER SECTIONS ALONG AXIALLY EXTENDING EDGES THEREOF INCLUDING A FLANGE ON EACH OF SAID EDGES HAVING A LATERALLY-BENT END PORTION AND A RADIALLY-EXTENDING MIDDLE PORTION, PAIRS OF CLIP MEMBERS, ONE MEMBER OF EACH PAIR OF CLIP MEMBERS BEING SECURED TO ONE OF AN ABUTTING CASING SECTION ADJACENT THE AXIALLY EXTENDING EDGE THEREOF, SAID CLIP MEMBERS HAVING OPPOSITELY-EXTENDING PORTIONS SPACED FROM AND PARALLEL TO THE INNER SURFACES OF SAID OUTER CASING SECTIONS TO FORM A CHANNEL THEREWITH, THE BENT END PORTIONS OF SAID LINER FLANGES BEING RECEIVED WITHIN SAID CHANNEL, WITH RESPECTIVE ONES OF SAID FLANGE BENT END PORTIONS BEING RADIALLY ALIGNED WITH RESPECTIVE CLIP MEMBER OPPOSITELYEXTENDING PORTIONS IN ORDER THAT RADIALLY-ALIGNED CASING AND LINER SECTIONS ARE REMOVABLE AS A UNIT, SAID SUPPORTING MEANS BEING ARRANGED AND LOCATED SO THAT SAID MIDDLE PORTIONS OF SAID FLANGES ARE NORMALLY IN ABUTMENT TO SEAL THE JOINT BETWEEN SAID LINER SECTION FLANGES AND SAID BENT END PORTIONS ARE CENTERED IN SAID CHANNEL TO CREATE FLOW PASSAGES FOR COOLING FLUID, SAID FLUID ACTING TO HELP MAINTAIN SAID FLANGES IN ABUTMENT. 